The invention relates to a method of manufacturing a cathode-ray tube, in which a cone having a edge and a substantially rectangular display window having a substantially rectangular sealing edge are positioned relative to each other and subsequently sealed to each other at the location of the sealing edge and the cone edge.
The invention further relates to a cathode-ray tube manufactured by such a method.
In the mass-production of cathode-ray tubes a number of parts, amongst others cones and display windows, are produced according to predetermined dimensions and configurations, after which a number of these parts are selected to be secured to each other. In order to obtain properly functioning cathode-ray tubes, it is necessary that the parts selected are accurately positioned relative to each other before being secured to one another. To position the cone and display window of a cathode-ray tube, prior to sealing use can be made of several reference systems. A commonly used reference system is described in U.S. Pat. 4,373,237. In this patent, reference surfaces are ground on the cone part and reference points are provided at the periphery of the display window. When the display window is positioned on the cone part, the reference points of the display window and the reference surfaces of the cone are referenced to a common reference. In this manner the display window is accurately positioned relative to the cone part. Other reference systems are described in, amongst others, German Offenlegungsschrift 2850602 and Netherlands Specifications 7909155 and 7304115 which are laid open to Public Inspection.
In general the display window is sealed to the cone edge at the location of the sealing edge by means of a glass frit provided on the cone edge before the display window and the cone are positioned relative to each other. After the display window has been accurately positioned on the cone, both are led through a sealing oven having a predetermined temperature schedule, where the glass frit is recrystallized, causing the display window and the cone to be sealed to each other in a vacuum-tight manner. In the course of this sealing process, temperature differences occur in the cathode-ray tube which cause tensile stresses in the cathode-ray tube. This may adversely affect the accurately adjusted positioning of the display window relative to the cone part.